A team of researchers from Argonne National
Laboratory (ANL) and the National Institute of Standards and
Technology (NIST) discovered key parameters within an advance
material that will enable the next-generation of
“spintronic” computers. Constructed by two
different compounds, this material promises to allow computers to
use the magnetic spin of electrons, in addition to their charge,
for computation. It also promises the use of fast memory devices
that can use considerably less power than conventional systems and
still retain data when the power is off.

Manganite oxide lattices (purple) doped
with lanthanum (magenta) and strontium (green) have potential for
use in spintronic memory devices, but their usual disorderly
arrangement (left) makes it difficult to explore their properties.
The ANL/NIST team’s use of a novel orderly lattice
(right) allowed them to measure some of the material’s
fundamental characteristics. (Credit: Argonne National
Laboratory.)

The team engineered a highly ordered version of
a magnetic oxide compound that naturally has two randomly
distributed elements: lanthanum and strontium. Stronger magnetic
properties are found in those places in the lattice where extra
lanthanum atoms are added. Precise placement of the strontium and
lanthanum within the lattice can enable understanding of what is
needed to harness the interaction of the magnetic forces among the
layers for memory storage applications, but such control has been
elusive up to this point.

So the ANL team was able to develop a method for
laying down the oxides one atomic layer at a time, allowing them to
construct an exceptionally organized lattice in which each layer
contains only strontium or lanthanum, so that the interface between
the two components could be studied. The NIST team members then
used the NCNR’s polarized neutron reflectometer to
analyze how the magnetic properties within this oxide lattice
changed as a consequence of the near-perfect placement of
atoms.

They found that the influence of electrons near
the additional lanthanum layers was spread out across three
magnetic layers in either direction, but fell off sharply further
away than that. Tiffany Santos, lead scientist on the study from
ANL, says that the measurement will be important for the emerging
field of oxide spintronics, as it reveals a fundamental size unit
for electronic and magnetic effects in memory devices made from the
material.

“For electrons to share spin
information — something required in a memory system
— they will need to be physically close enough to
influence each other,” Kirby says. “By ordering
this material in such a precise way, we were able to see just how
big that range of influence is.”